1. Field of the Invention
The invention relates to semiconductor devices having metal gate and a manufacturing method thereof, and more particularly, to integrated semiconductor devices having metal gate and a manufacturing method thereof.
2. Description of the Prior Art
With rapid advancement of semiconductor fabricating technology, the integration level of integrated circuits (ICs) is bound to increase continuously in order to improve the device speed and performance and to comply with current requirements for light weight, slimness, and compactness. Improvement of the integration level is inevitably relies on reducing size of feature patterns and pitches between features patterns which construct the devices and ICs. However, size and/or pitch reduction increases difficulty and complexity of device productions.
On the other hand, field effect transistor (hereinafter abbreviated as FET) devices are essential elements of the IC(s) and parameters of the FET devices such as drain-source on resistance (RDson), drain-source breakdown voltage (BVds), and threshold voltage (Vt) significantly influence operation and performance of the FET devices. Furthermore, IC(s) may be constructed by devices of different threshold voltages or different breakdown voltages, and thus requirement of multi-function is complied.
Therefore it is always in need to build up IC(s) including not only superior performance, but also superior multi-functionalities.